wm: Update a lot of code to use structs from geometry.h.

geometry.h

Index: geometry.h
diff --git a/geometry.h b/geometry.h
index d214ce79a951065512449b8209b8dcbb3d934302..9091e8b614a263aee64c6084aa8d07e2ae763649 100644
--- a/geometry.h
+++ b/geometry.h
@@ -56,6 +56,9 @@ struct Size {
     height = new_height;
   }
 
+  bool empty() const { return width <= 0 || height <= 0; }
+  int area() const { return empty() ? 0 : width * height; }
+
   bool operator==(const Size& o) const {
     return width == o.width && height == o.height;
   }
@@ -135,6 +138,13 @@ struct Rect {
     height = std::max(0, max_y - y);
   }
 
+  bool contains_point(const Point& point) const {
+    return point.x >= x &&
+           point.x < x + width &&
+           point.y >= y &&
+           point.y < y + height;
+  }
+
   bool operator==(const Rect& o) const {
     return x == o.x && y == o.y && width == o.width && height == o.height;
   }